# A beam of red light has twice the intensity as a second bean of the same color

## Homework Statement

A beam of red light has twice the intensity as a second bean of the same color. Calculate the ratio of the amplitude of wave.

## Homework Equations

$$intensity \propto (amplitude)^2$$

## The Attempt at a Solution

$$1^{st} \mbox{ beam} = 2I$$
$$2^{nd} \mbox{ beam} = I$$

I don't know if this step is correct and I don't know what to do next?!

## Homework Equations

$$intensity \propto (amplitude)^2$$

## The Attempt at a Solution

$$1^{st} \mbox{ beam} = 2I$$
$$2^{nd} \mbox{ beam} = I$$
$$I_1=2 I_2$$

$$\frac{I_1}{I_2}=2$$

What can you do to the above relation (given your relevant equation) to convert it to a ratio of amplitudes?

Regards,

Bill

$$intensity \propto (amplitude)^2$$

So, it will be $$1:4$$ ?

Defennder
Homework Helper
No, start off by expressing both intensities I = kA^2. Then compare the ratio of each amplitude to the other.

$$intensity \propto (amplitude)^2$$

So, it will be $$1:4$$ ?
No. Try what Defennder suggested to see why.

Regards,

Bill